Conventional fluid pumps are well known. Although conventional fluid pumps are readily available in both low and high capacity designs, a common feature is that they have many moving parts that create noise and vibration. Also, there are reliability and lifetime limitations due to normal wear phenomena. Furthermore, because conventional pumps have multiple parts, they tend to be large, heavy and expensive.
Micropumps, also known as miniature pumps, are pumps that are fabricated on a microchip utilizing micromachining processes. For small capacity requirements, micropumps provide improved reliability with fewer parts. For example, micropumps utilizing electroactive transducers have emerged for biomedical and metering applications where small pressures and flow rates are required and where conventional pumps are somewhat impractical. The typical capacity of a micropump may be in the range of a few nano liters per second to a few micro liters per second. Since the total fluid power output of these devices is very small, efficiency is not highly important and is generally low. The relatively low efficiency of the micropump makes massive parallel arraying of many micropumps unattractive as a way of competing with larger conventional pumps. Scaling up the size and pressure of such electroactively driven devices does not improve the efficiency and is difficult due to on-chip fabrication techniques. This class of pump is therefore not able to compete directly with larger conventional pump designs for large fluid output.
Micro Electro Mechanical System (MEMS) microvalve arrays are known and are utilized to achieve precision fluid flow control. In a microvalve array, multiple diaphragms cover multiple ports to restrict and control fluid flow. In some designs, heaters can be activated to warm and expand a closed fluid volume that in turn moves diaphragms to close and open the individual ports to achieve a desired flow. This arrangement permits precise flow rate control but is slow to respond due to thermal conduction to and from the closed fluid volume. Other activation methods, such as piezoelectric activation, can provide faster opening and closing of the ports.
What is needed is a compact, high capacity pump that has minimal moving parts, is able to handle a relatively large fluid output, and has improved operating efficiency and reliability as well as reduced weight, size and cost.